1. Field of the Invention
This invention relates to a magnetoresistance effect device exhibiting an especially high magnetoresistance effect, a magnetic memory display/input apparatus, and a method for manufacturing them, a magnetic head, and a magnetic recording apparatus including the magnetic head.
2. Background Art
Recently, magnetic recording density in hard disk drives has rapidly increased, and reproducing sensitivity and reproducing resolution required for the reproducing head have also increased accordingly year by year. The advent of the GMR (giant magnetoresistance effect) head operating on the principle of spin-dependent scattering has dramatically enhanced the output and has been adapted to the increase of recording density. Furthermore, reproducing device structures are proposed for responding to higher recording density.
More recently, nonvolatile solid memory devices have been reported in which domain walls in a metal magnetic material are treated as information. The magnetic moment is determined on the basis of electron spin information, and a domain wall is formed at the boundary of the spin information. Hence studies have been vigorously pursued to drive a domain wall by electron current, which is more adaptable to downscaling, instead of the conventional technique of driving a domain wall by magnetic field.
JP-A 2002-270922 (Kokai) discloses a magnetoresistance device in which a magnetic body having a constricted structure is provided between two magnetic bodies.
There is another device in which a domain wall is confined in a wire having two, large and small, magnetic “constrictions”. The large constriction has a low resistance (information “0”), and the small constriction has a high resistance (information “1”). Rewriting between “0” and “1” is conducted by moving a domain wall between the constrictions by current drive. The inventor confirmed a magnetoresistance effect (MR) of approximately 10 to 20% at a point contact that is formed by two-dimensionally and three-dimensionally constricting a sputtered NiFe (permalloy) film by ion milling (Y. Ohsawa, “Current-driven resistance change and magnetoresistance measurements in NiFe films with a nanoconstriction”, IEEE Trans. Magn., vol. 42, No. 10, p. 2615 (2006); Y. Ohsawa, “In-situ magnetoresistance measurements of a nanoconstricted NiFe film with in-plane configuration”, IEEE Trans. Magn., vol. 41, No. 10, p. 2577 (2005)).
In these disclosed techniques, a magnetic body is patterned to form a point contact. However, even by the latest lithography technique, it is not easy to form an ideal point contact with good reproducibility, and there is no further enhancement in the magnetoresistance effect.
On the other hand, JP-A 2004-342167 (Kokai) discloses a manufacturing method in which an insulating film is sandwiched on both sides between magnetic layers, which are interconnected by a discontinuous magnetic film, thereby connecting between the upper and lower magnetic layers at a small contact. In this disclosed technique, on a magnetic sensitive layer are formed an insulating section and a reference magnetic section, which are smaller in area than the magnetic sensitive layer. Magnetic bodies are formed on the reference magnetic section and the magnetic sensitive section. As the amount of formation of the magnetic bodies is gradually increased, a portion arises where the stepped portion between the magnetic sensitive section and the reference magnetic section becomes conducting through the formed magnetic bodies. This conducting portion is used as a small contact. Then a domain control section and an upper electrode are formed on the reference magnetic section.
However, in this disclosed technique, the magnetic body serving as a small contact is sandwiched between the reference magnetic section and the domain control section.